Abstract : The optical properties of thin semi-transparent amorphous Co-P and Ni-P alloy films prepared by flash-evaporation under vacuum are determined over a large energy range. They are compared to those of pure Co and Ni films on the one hand, of crystalline Co2P and Ni3P films on the other hand. The similarities observed between the optical spectra of the amorphous alloys and of the crystalline compounds suggest the presence of local atomic arrangements of the Co2P and Ni3P type in the amorphous state. Our results tend to question the validity of a simple nearly-free electron model and is in favour of an hybridization of the P p-states with the transition metal d-states in these amorphous metallic alloys.